Bugzilla bug 219487: fixed build failure on OpenVMS. struct addrinfo is

defined in <netdb.h>.  We use AI_CANONNAME, a macro to be used with struct
addrinfo, to detect that.

nsprpub/pr/include/md/_openvms.h

@@ -111,6 +111,8 @@ struct ip_mreq {
 #define _PR_HAVE_INET_NTOP
 #else
 #define AF_INET6 26
+#ifndef AI_CANONNAME
+#define AI_CANONNAME 0x00000002
 struct addrinfo {
     int ai_flags;
     int ai_family;
@@ -121,7 +123,7 @@ struct addrinfo {
     struct sockaddr *ai_addr;
     struct addrinfo *ai_next;
 };
-#define AI_CANONNAME 0x00000002
+#endif
 #define AI_V4MAPPED 0x00000010
 #define AI_ALL      0x00000008
 #define AI_ADDRCONFIG 0x00000020